Hippocampal‐sparing whole‐brain radiotherapy using the Elekta equipment

Abstract

The purpose of this study was to evaluate the feasibility of hippocampal‐sparing whole‐brain radiotherapy (HS WBRT) using the Elekta Infinity linear accelerator and Monaco treatment planning system (TPS). Ten treatment plans were created for HS‐WBRT to a dose of 30 Gy (10 fractions). RTOG 0933 recommendations were applied for treatment planning. Intensity‐modulated radiotherapy (IMRT) plans for the Elekta Infinity linear accelerator were created using Monaco 3.1 TPS‐based on a nine‐field arrangement and step‐and‐shoot delivery method. Plan evaluation was performed using D2% and D98% for the whole‐brain PTV (defined as whole brain excluding hippocampus avoidance region), D100% and maximum dose to the hippocampus, and maximum dose to optic nerves and chiasm. Homogeneity index (HI) defined as false(D2normal%−D98normal%false)/normalDmedian was used to quantify dose homogeneity in the PTV. The whole‐brain PTV D2% mean value was 37.28 Gy (range 36.95–37.49 Gy), and D98% mean value was 25.37 Gy (range 25.40–25.89 Gy). The hippocampus D100% mean value was 8.37 Gy (range 7.48–8.97 Gy) and the hippocampus maximum dose mean value was 14.35 Gy (range 13.48–15.40 Gy). The maximum dose to optic nerves and optic chiasm for all patients did not exceed 37.50 Gy. HI mean value was 0.36 (range 0.34–0.37). Mean number of segments was 105 (range 88–122) and mean number of monitor units was 1724 (range 1622–1914). Gamma evaluation showed that all plans passed 3%, 3 mm criteria with more than 99% of the measured points. These results indicate that Elekta equipment (Elekta Infinity linac and Monaco TPS) can be used for HS WBRT planning according to compliance criteria defined by the RTOG 0933 protocol.PACS numbers: 87.55D, 87.55 –v, 87.55 de

Potential for reduced radiation‐induced toxicity using intensity‐modulated arc therapy for whole‐brain radiotherapy with hippocampal sparing

“…However, no treatment time was reported. Another study presented by Nevelsky et al (12) used Elekta equipment with nine noncoplanar IMRT beams and Monaco TPS to spare hippocampus. Following the RTOG guidelines, in 10 patient plans, Nevelsky and colleagues have shown dose to 100% of hippocampus 8.4 Gy, on average, and the hippocampus maximum dose mean value 14.4 Gy with an excellent IMRT QA results.…”

“…(6) However, clinical and preclinical evidence suggest that irradiating a neural stem cell compartment in the hippocampus introduces radiation-induced neurocognitive toxicity/deficits (short-and long-term memory loss) after conventional nonconformal WBRT within the first one to four months, leading to compromise in QoL. (7,8,9) To address this issue, researchers have developed helical tomotherapy (10,11) or linear acceleratorbased, intensity-modulated radiation therapy (IMRT) techniques (11,12) with hippocampal sparing that could conformally avoid the hippocampi and significantly reduce the amount of radiation dose to the neural stem cell compartment in the hippocampus. However, tomotherapy or linear accelerator-based IMRT requires a large number of total MUs and relatively longer treatment times.…”

“…However, tomotherapy or linear accelerator-based IMRT requires a large number of total MUs and relatively longer treatment times. (10,11,12) A recently introduced rotational radiotherapy technique, intensity-modulated arc therapy (IMAT) treatment planning system, delivers a highly conformal radiation dose to the target by simultaneously modulating gantry rotation, dose rate, and multileaf collimators (MLCs) position. (13,14,15,16,17) The advantages of the IMAT system over IMRT include the ability to reduce the total number of MUs and subsequently the beam-on time, which may improve patient tolerance of treatment, and potentially reduce leakage radiation dose to the patients.…”

Efficiency of biological versus physical optimization for single‐arc VMAT for prostate and head and neck cases

“…In our opinion, possible expected gain in doses to OARs in highly complex plans with use of biological cost functions in Monaco was compromised by VMAT sequencer in this version of TPS, as also noticed in the paper by Nevelsky at al (28) . Hence speed of the treatment delivery is reduced with VMAT by approximately 60% (2,4,5,10) .…”

Benefits and difficulties during brain radiotherapy planning with hippocampus sparing

“…On the other hand, the majority of research on the hippocampus protection procedure during cerebral irradiation concerns patients with BM. Unfortunately, the current results of the study do not allow us to clearly define the eligibility criteria for the hippocampus protection procedure during brain RT in the above group of patients [52][53][54].…”